交易调用数据解密 - 理解以太坊交易调用数据的指南

概述

如果你之前与以太坊上的智能合约互动过，你可能注意到你的交易包括一个在数据字段中的长十六进制值。作为用户（或开发者），你可能希望更好地理解这些值。本指南将正是涵盖这一点——你将学习如何解码交易的 calldata，以便更好地理解你遇到的其他交易。在本指南结束时，你还将学习如何在程序中使用 Web3.py 和 Python 进行编码和解码。

你需要的准备

• 对以太坊的基本理解
• 推荐了解：以太坊交易是什么？
• 推荐阅读：以太坊智能合约概述
• 已安装 Web3.py

你将做的事情

• 学习如何编码和解码交易 calldata
• 创建一个以太坊端点（在 这里注册免费账户）
• 使用 Web3.py 对交易 calldata 进行编码和解码

什么是交易 Calldata？

交易 calldata 是随交易传递的数据，允许我们向其他实体发送消息或与智能合约互动。

交易 calldata 看起来是什么样的？以下是一个以太坊上的交易，这是一次 DAI 转账，包括 calldata（即 输入数据 字段）

来源：Etherscan

Etherscan 为我们格式化此 calldata，这样更易于理解。但是，实际的原始交易 calldata 将如下所示：

0xa9059cbb0000000000000000000000003f5047bdb647dc39c88625e17bdbffee905a9f4400000000000000000000000000000000000000000000011c9a62d04ed0c80000

你可能想知道这些十六进制值代表什么。别担心。到本指南结束时，你将确切知道如何解密以太坊（和其他 EVM 基链）的交易 calldata！

解码 Calldata

在解码上述 calldata 之前，让我们回顾一些基本规则。

• Calldata 是可以变长的字节数组（但受区块 gas 限制）
• Calldata 可以包含以静态或动态格式表示的数据

一些静态 calldata 的示例是 addresses、uint、bytes32 和 bool 类型，它们是固定长度的。

• addresses：长度为 20 字节或 40 个字符
• uint256：长度为 32 字节或 64 个字符
• bytes32：固定大小的字节数组，32 字节（即 64 个字符长）
• bool：长度为 1 字节或 1 个字符

而动态变量，例如 bytes 和 int[]，等，是不固定长度的。考虑到这些概念，让我们尝试解码上述交易 calldata。

在 引用的交易 中被调用的函数是 transfer，其定义为 transfer(address dst, uint256 wad)。再次强调，原始 calldata 由以下内容组成：

0xa9059cbb0000000000000000000000003f5047bdb647dc39c88625e17bdbffee905a9f4400000000000000000000000000000000000000000000011c9a62d04ed0c80000

让我们将其拆解。

• calldata 的第一部分 0x 让我们知道该值是十六进制
• 接下来的四个字节是 a9059cbb，这指的是函数选择器，通过对函数名称及其输入类型的 sha3 哈希的前 4 个字节进行计算生成。用于识别所调用的函数。查看 ABI 规范。
• 下一组字节是 0000000000000000000000003f5047bdb647dc39c88625e17bdbffee905a9f44，长度为 64 个字符，表示 address dst 输入。000000000000000000000000 表示用于确保值占用相同内存量的填充。剩余字节指的是接收地址 3f5047bdb647dc39c88625e17bdbffee905a9f44。
• 下一组字节是 00000000000000000000000000000000000000000000011c9a62d04ed0c80000，它指的是 uint256 wad 输入。我们应期望它为 32 字节（或 64 个字符长度）。000000000000000000000000000000000000000000000 是填充，剩余的 11c9a62d04ed0c8 指的是 Wei 值的金额，该金额转换并除以 18 位小数后，即为 5250。而余下的 0000 是尾随零，以确保数据总是 32 字节长。

使用 Python 解码 Calldata

在我们开始之前，我们需要访问一个以太坊节点。你可以使用公有节点或部署并管理自己的基础设施；但是，如果你想要 8 倍更快的响应时间，可以将重任交给我们。注册一个免费账户 这里。

登录后，点击 创建端点 并选择以太坊主网链。

端点创建完成后，保留 HTTP 提供者 URL，因为在 Python 脚本中需要它。

现在，在 Python 中，你可以使用 Web3.py 库及以下代码解码相同的 calldata：

from web3 import Web3

## RPC URL
w3 = Web3(Web3.HTTPProvider("QUICKNODE_ETHEREUM_ENDPOINT"))

## DAI 合约地址
contract_address = '0x6B175474E89094C44Da98b954EedeAC495271d0F'

## DAI 合约 ABI
abi = '[{"inputs":[{"internalType":"uint256","name":"chainId_","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"constructor"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"src","type":"address"},{"indexed":true,"internalType":"address","name":"guy","type":"address"},{"indexed":false,"internalType":"uint256","name":"wad","type":"uint256"}],"name":"Approval","type":"event"},{"anonymous":true,"inputs":[{"indexed":true,"internalType":"bytes4","name":"sig","type":"bytes4"},{"indexed":true,"internalType":"address","name":"usr","type":"address"},{"indexed":true,"internalType":"bytes32","name":"arg1","type":"bytes32"},{"indexed":true,"internalType":"bytes32","name":"arg2","type":"bytes32"},{"indexed":false,"internalType":"bytes","name":"data","type":"bytes"}],"name":"LogNote","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"src","type":"address"},{"indexed":true,"internalType":"address","name":"dst","type":"address"},{"indexed":false,"internalType":"uint256","name":"wad","type":"uint256"}],"name":"Transfer","type":"event"},{"constant":true,"inputs":[],"name":"DOMAIN_SEPARATOR","outputs":[{"internalType":"bytes32","name":"","type":"bytes32"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"PERMIT_TYPEHASH","outputs":[{"internalType":"bytes32","name":"","type":"bytes32"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"internalType":"address","name":"","type":"address"},{"internalType":"address","name":"","type":"address"}],"name":"allowance","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"usr","type":"address"},{"internalType":"uint256","name":"wad","type":"uint256"}],"name":"approve","outputs":[{"internalType":"bool","name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[{"internalType":"address","name":"","type":"address"}],"name":"balanceOf","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"usr","type":"address"},{"internalType":"uint256","name":"wad","type":"uint256"}],"name":"burn","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"decimals","outputs":[{"internalType":"uint8","name":"","type":"uint8"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"guy","type":"address"}],"name":"deny","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"usr","type":"address"},{"internalType":"uint256","name":"wad","type":"uint256"}],"name":"mint","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"src","type":"address"},{"internalType":"address","name":"dst","type":"address"},{"internalType":"uint256","name":"wad","type":"uint256"}],"name":"move","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"name","outputs":[{"internalType":"string","name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"internalType":"address","name":"","type":"address"}],"name":"nonces","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"holder","type":"address"},{"internalType":"address","name":"spender","type":"address"},{"internalType":"uint256","name":"nonce","type":"uint256"},{"internalType":"uint256","name":"expiry","type":"uint256"},{"internalType":"bool","name":"allowed","type":"bool"},{"internalType":"uint8","name":"v","type":"uint8"},{"internalType":"bytes32","name":"r","type":"bytes32"},{"internalType":"bytes32","name":"s","type":"bytes32"}],"name":"permit","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"usr","type":"address"},{"internalType":"uint256","name":"wad","type":"uint256"}],"name":"pull","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"usr","type":"address"},{"internalType":"uint256","name":"wad","type":"uint256"}],"name":"push","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"guy","type":"address"}],"name":"rely","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"symbol","outputs":[{"internalType":"string","name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"totalSupply","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"dst","type":"address"},{"internalType":"uint256","name":"wad","type":"uint256"}],"name":"transfer","outputs":[{"internalType":"bool","name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"src","type":"address"},{"internalType":"address","name":"dst","type":"address"},{"internalType":"uint256","name":"wad","type":"uint256"}],"name":"transferFrom","outputs":[{"internalType":"bool","name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"version","outputs":[{"internalType":"string","name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"internalType":"address","name":"","type":"address"}],"name":"wards","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"}]'

## 合约对象
contract = w3.eth.contract(address=contract_address, abi=abi)

## 要解码的原始调用数据
data = "0xa9059cbb0000000000000000000000003f5047bdb647dc39c88625e17bdbffee905a9f4400000000000000000000000000000000000000000000011c9a62d04ed0c80000"

## 解码调用数据
decoded_data = contract.decode_function_input(data)

## 打印解码后的调用数据
print(decoded_data)

结果将如下所示：

(<Function transfer(address,uint256)>, {'dst': '0x3F5047BDb647Dc39C88625E17BDBffee905A9F44', 'wad': 5250000000000000000000})

给自己点个赞，因为你已经学会了理解以太坊交易 calldata 的难点！下一部分将介绍如何编码 calldata。

使用 Python 编码 Calldata

参照相同的交易合约，我们可以使用以下 Python 代码编码 transfer 函数及其有效载荷：

from web3 import Web3

## RPC url
w3 = Web3(Web3.HTTPProvider("QUICKNODE_ETHEREUM_ENDPOINT"))

## 要调用的函数的 ABI
abi = '[{"inputs":[{"internalType":"uint256","name":"chainId_","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"constructor"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"src","type":"address"},{"indexed":true,"internalType":"address","name":"guy","type":"address"},{"indexed":false,"internalType":"uint256","name":"wad","type":"uint256"}],"name":"Approval","type":"event"},{"anonymous":true,"inputs":[{"indexed":true,"internalType":"bytes4","name":"sig","type":"bytes4"},{"indexed":true,"internalType":"address","name":"usr","type":"address"},{"indexed":true,"internalType":"bytes32","name":"arg1","type":"bytes32"},{"indexed":true,"internalType":"bytes32","name":"arg2","type":"bytes32"},{"indexed":false,"internalType":"bytes","name":"data","type":"bytes"}],"name":"LogNote","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"src","type":"address"},{"indexed":true,"internalType":"address","name":"dst","type":"address"},{"indexed":false,"internalType":"uint256","name":"wad","type":"uint256"}],"name":"Transfer","type":"event"},{"constant":true,"inputs":[],"name":"DOMAIN_SEPARATOR","outputs":[{"internalType":"bytes32","name":"","type":"bytes32"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"PERMIT_TYPEHASH","outputs":[{"internalType":"bytes32","name":"","type":"bytes32"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"internalType":"address","name":"","type":"address"},{"internalType":"address","name":"","type":"address"}],"name":"allowance","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"usr","type":"address"},{"internalType":"uint256","name":"wad","type":"uint256"}],"name":"approve","outputs":[{"internalType":"bool","name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[{"internalType":"address","name":"","type":"address"}],"name":"balanceOf","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"usr","type":"address"},{"internalType":"uint256","name":"wad","type":"uint256"}],"name":"burn","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"decimals","outputs":[{"internalType":"uint8","name":"","type":"uint8"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"guy","type":"address"}],"name":"deny","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"usr","type":"address"},{"internalType":"uint256","name":"wad","type":"uint256"}],"name":"mint","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"src","type":"address"},{"internalType":"address","name":"dst","type":"address"},{"internalType":"uint256","name":"wad","type":"uint256"}],"name":"move","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"name","outputs":[{"internalType":"string","name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"internalType":"address","name":"","type":"address"}],"name":"nonces","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"holder","type":"address"},{"internalType":"address","name":"spender","type":"address"},{"internalType":"uint256","name":"nonce","type":"uint256"},{"internalType":"uint256","name":"expiry","type":"uint256"},{"internalType":"bool","name":"allowed","type":"bool"},{"internalType":"uint8","name":"v","type":"uint8"},{"internalType":"bytes32","name":"r","type":"bytes32"},{"internalType":"bytes32","name":"s","type":"bytes32"}],"name":"permit","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"usr","type":"address"},{"internalType":"uint256","name":"wad","type":"uint256"}],"name":"pull","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"usr","type":"address"},{"internalType":"uint256","name":"wad","type":"uint256"}],"name":"push","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"guy","type":"address"}],"name":"rely","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"symbol","outputs":[{"internalType":"string","name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"totalSupply","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"dst","type":"address"},{"internalType":"uint256","name":"wad","type":"uint256"}],"name":"transfer","outputs":[{"internalType":"bool","name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"src","type":"address"},{"internalType":"address","name":"dst","type":"address"},{"internalType":"uint256","name":"wad","type":"uint256"}],"name":"transferFrom","outputs":[{"internalType":"bool","name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"version","outputs":[{"internalType":"string","name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"internalType":"address","name":"","type":"address"}],"name":"wards","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"}]'

## 合约地址
contract_address = '0x6B175474E89094C44Da98b954EedeAC495271d0F'

## 合约对象
contract = w3.eth.contract(address=contract_address, abi=abi)

## 编码函数调用
function_name = 'transfer'
args = ["0x3f5047bdb647dc39c88625e17bdbffee905a9f44", 5250000000000000000000]
encoded_data = contract.encodeABI(fn_name=function_name, args=args)

## 打印编码后的数据
print(encoded_data)

结果将看起来与 引用的交易 中包含的原始交易 calldata 一样。

结论

就是这样！你现在知道如何理解以太坊的交易 calldata，如何使用 Python 轻松编码和解码交易。检查一下其他 以太坊开发 和 智能合约开发 指南。

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• 原文链接： quicknode.com/guides/eth...
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